The WeighTrainer

Weight Loss Calorie Calculator

The numbers below represent the daily caloric requirement of your body and the daily caloric intake necessary to lose the weekly amount specified, based on your weight, percent bodyfat and activity level. They are approximations only (based on the Katch-McArdle formula). Generally, the estimates will be accurate to within 14% of actual values.

In addition, the calculator estimates the maximum amount of fat loss that you, at your current bodyfat level, can support without losing lean body mass (i.e. muscle). It is based on S.S. Alpert, "A limit on the energy transfer rate from the human fat store in hypophagia.", J. Theor. Biol. 2005, Mar 7; 233(1); though I first came across it in an article by Lyle McDonald.

The amount of protein required to support muscle maintenance and growth (possibly) while dieting is estimated (as calculated from research involving drug-free bodybuilders), along with the amount of dietary fat to maximize testosterone production, and the dietary carbohydrates which make up the remainder of the diet.

All of these calculations assume that you haven't already slowed your metabolism with prolonged and/or extreme dieting.